Air compressors used to provide compressed air for operating air powered tools such as nailing tools, spray painting tools, inflation chucks, and the like typically include an engine or motor coupled to a compressor and mounted to a compressed air storage tank. The compressor includes a head assembly, connecting tubing and a check valve that supplies atmospheric air to the piston assembly and delivers compressed air from the piston assembly to the compressed air storage tank.
Before the compressor is started, it is desirable to relieve pressure from the exhaust cavity of the head assembly to reduce the load placed on the engine or motor. Consequently, air compressors usually include a valve, commonly referred to as the pressure switch unloader valve, and a pressure relief tube, which allow air to be vented from the head assembly to the atmosphere when the compressor is turned off.
In many applications, it is desirable to simplify the design of an air compressor in order to realize savings in manufacturing costs, maintenance costs, weight, and the like. In such applications, it may be advantageous to reduce the complexity of the air compressor by eliminating the pressure switch unloader and pressure relief tube. Consequently, it would be advantageous to provide a mechanism by which pressure may be vented from the head assembly. It would further be desirable to vent this pressure when the compressor is not running, but to prevent such venting when the compressor is running.